= Inward transport by an angular-momentum-enhanced disk wind
{title2=$x'=\int\frac{dr}{\beta rf},\quad g'=fr^{2-1/\beta}\Sigma,\quad g'_t=g'_{x'}$}
For zero viscosity, $S=f(r)\Sigma$ and constant $q>1$, set $\beta=2(q-1)$. On intervals where f>0, the <wind-loaded Keplerian disk evolution> equation becomes $\Sigma_t=\beta rf\Sigma_r+[\beta(2f+rf')-f]\Sigma$. Multiplication by $fr^{2-1/\beta}$ and the displayed travel-time coordinate reduce it to constant-speed <advection>. Its profile is $g'=F(x'+t)$ and its characteristics move inward with $dr/dt=-\beta rf$. The weight accounts for mass loss as well as radial compression.
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